GaN Crystal Impurity Reduction via Oxidation-Etching
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Solution Overview
Problem
Existing methods for growing group-III nitride crystals, such as gallium nitride (GaN), struggle to achieve high purity with extremely low concentrations of impurities like silicon (Si), boron (B), iron (Fe), oxygen (O), and carbon (C), which are essential for improving semiconductor device quality and yield.
Innovation Solution
A high temperature baking step is introduced where an oxidizing sequence and an etching sequence are alternately repeated in the crystal growth furnace, using gases like oxygen (O2) and hydrogen chloride (HCl) to reduce the concentrations of O and C to less than 1×10^15 at/cm3 over 60% or more of the crystal's surface, resulting in a GaN crystal with enhanced hardness and insulation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional crystal growth methods are used, then manufacturing process is simple, but impurity concentration cannot be reduced below 1×10^15 at/cm3
Solution Approach 1:
The patent applies preliminary action by performing a high-temperature baking step (1000-1500°C) in the crystal growth furnace before actual crystal growth to remove organic contaminants and reduce impurity concentrations. This preliminary cleaning action prepares the furnace environment to achieve ultra-low impurity levels (below 1×10^15 at/cm3) in the grown crystals.
Solution Approach 2:
The patent implements periodic action through alternating oxidizing sequences (using O2 or air) and etching sequences (using HCl gas) during the high-temperature baking step. This periodic alternation between oxidation and etching effectively removes organic impurities and reduces carbon contamination, achieving the target impurity concentration level.
2Manufacturing precision
If high temperature baking with oxidizing and etching sequences is applied, then impurity concentration is reduced to below 1×10^15 at/cm3, but manufacturing process complexity increases
Solution Approach 1:
The patent merges the high-temperature baking step with the existing crystal growth furnace, combining the impurity removal function with the crystal growth function in a single equipment system. This integration allows the complex multi-step process (oxidizing-etching cycles at high temperature) to be performed without requiring additional specialized equipment, thus managing manufacturing complexity while achieving ultra-low impurity concentrations.
3Reliability
If impurity concentration is reduced to below 1×10^15 at/cm3, then crystal quality and semiconductor device performance improve, but manufacturing time and process steps increase
Solution Approach 1:
The high-temperature baking step with alternating oxidizing and etching sequences is performed as a preliminary action before crystal growth to reduce impurity concentrations below 1×10^15 at/cm3. This preliminary treatment ensures ultra-high crystal quality and reliability from the outset, preventing impurity-related defects in semiconductor devices without requiring additional post-processing steps.
Solution Approach 2:
The patent employs parameter changes by conducting the high-temperature baking step at 1000-1500°C with controlled gas flow rates and alternating sequences. These optimized parameters enable effective impurity removal within a reasonable time frame, achieving the balance between manufacturing cycle time and crystal quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach significantly reduces impurity concentrations, leading to improved crystal quality, increased hardness exceeding 22 GPa, and high insulation properties, thereby enhancing the performance and yield of semiconductor devices manufactured using these crystals.
Implementation Method 1
an oxidizing sequence and an etching sequence are alternately repeated in the crystal growth furnace, using gases like oxygen (O2)
Implementation Method 2
an oxidizing sequence and an etching sequence are alternately repeated in the crystal growth furnace, using gases like oxygen (O2) and hydrogen chloride (HCl)
Implementation Method 3
A high temperature baking step is introduced where an oxidizing sequence and an etching sequence are alternately repeated
Data Source
AI summary
An object of the present invention is to improve quality of a nitride crystal, and also improve performance and manufacturing yield of a semiconductor device manufactured using the crystal. Provided is a nitride crystal in which a composition formula is represented by InxAlyGa1-x-yN (satisfying 0≤x≤1, 0≤y≤1, 0≤x+y≤1), and the concentration of B in the crystal is less than 1×1015 at/cm3, and each of the concentrations of O and C in the crystal is less than 1×1015 at/cm3 in a region of 60% or more of a main surface.